etween the birds of the East and those of the West. Why does the hardy and almost ubiquitous blue jay studiously avoid the western plains and mountains? Why do not the magpie and the long-crested jay come east? What is there that prevents the indigo-bird from taking up residence in Colorado, where his pretty western cousin, the lazuli finch, finds himself so much at home? Why is the yellow-shafted flicker of the East replaced in the West by the red-shafted flicker? These questions are more easily asked than answered. From the writer's present home in eastern Kansas it is only six hundred miles to the foot of the Rockies; yet the avi-fauna of eastern Kansas is much more like that of the Eastern and New England States than that of the Colorado region.

Perhaps the reason is largely, if not chiefly, physiological. Evidently there are birds that flourish best in a rare, dry atmosphere, while others naturally thrive in an atmosphere that is denser and more humid. The same is true of people. Many persons find